Shunt trip with load terminal

ABSTRACT

A compact circuit breaker having automatic overload protection is provided with a shunt tripping coil that generates flux to release the same latch acted upon by the overload protection means. The shunt trip coil within the circuit breaker is connected to a shunt lead, extending from the breaker, and to the conventional load terminal. Typically, external of the breaker the shunt lead is connected to neutral through a normally open pushbutton switch and voltage is removed from the shunt trip coil when the breaker opens.

United States Patent Gryctko et al.

[ 1 Nov. 21, 1972 [54] SHUNT TRIP WITH LOAD TERMINAL [72] Inventors: Carl E. Gryctko, Haddon Heights, N'.J.; Howard R. Shaffer, Glenside, Pa.

[73] Assignee: l-T-E Imperial Corporation,

Philadelphia, Pa.

[22] Filed: Aug. 31, 1971 {21 App]. No.: 176,641

52] US. Cl ..'.335/20, 335/172 [51] Int. Cl. ..ll0lh 83/10 [58] Field of Search 335/20, 8, 9, 173, 13,172

[56] References Cited UNITED STATES PATENTS 3,319,196 5/1967 Myers ..335/172 3,369,202 '2/1968 Gryctko ..335/9 3,256,407 6/1966 Klein ..335/173 3,436,695 4/1969 Dessert ..335/13 Primary ExaminerHar0ld Broome Attorney-Sidney G. Faber et al.

[57 ABSTRACT A compact circuit breaker having automatic overload protection is provided with a shunt tripping coil that generates flux to release the same latch acted upon by the overload protection means. The shunt trip coil within the circuit breaker is connected to a shunt lead, extending from the breaker, and to the conventional load terminal. Typically, external of the breaker the shunt lead is connected to neutral through a normally open pushbutton switch and voltage is removed from the shunt trip coil when the breaker opens.

10 Claims, 4 Drawing Figures SHUNT TRIP WITH LOAD. TERMINAL This invention relates to circuit breakers in general, and more particularly'relates to a load current carrying single pole unit havingoverload protection and'shunt trip means.

Branch circuit breakers used in panelboards for the home and light industrial applications are extremely compact units which usually include overload protecting automatic tripping means, For some applications it is required that one or more of these branch circuit breakers be controlled ata location remote from the panelboard. V

In the prior art, remote or shunt tripping of this type of circuit breaker was usually accomplished by having the overload trip device in one pole and having a shunt trip device and its auxiliary switch in another pole, with these poles being mechanically interlocked so that the tripping of the shunt trip device automatically tripped the pole carrying the load current. This type of prior art arrangement is shown in U.S. Pat. No. 3,369,202 issued Feb. 13, 1968 to C. E. Gryctko and entitled Circuit Breaker Stack Including Auxiliary Features. I

In accordance with the instant invention, a standard size single pole low current circuit breaker is provided with both overload and shunt tripping features. This is accomplished by a slight modification of the now standard-type circuit breaker mechanism illustrated in U.S. Pat. No. 2,996,589 issued Aug. 15, 1961 to F. E. Myers and entitled Pivoted Bimetal.

More particularly, in one embodiment of the instant invention the overload tripping bimetal carries the resettable latch for the contact operating mechanism and is electrically connected directly to the load terminal. The shunt trip device includes a magnet, which when actuated is effective to release the latch. The coil of the electromagnet is connected at one end directly to the load terminal, and at the other end is provided with a flexible lead that extends through the circuit breaker housing at the load end thereof.

In another embodiment of the instant invention, a common coil for the electromagnet is used to carry load current and provide means for automatic tripping under severe overload conditions. This same coil, one end of which is connected directly to the load terminal, acts as the shunt trip coil.

' In still another embodiment of this invention, the tripping electromagnet is provided with a two-section coil, one end of one coil is connected in circuit with the tripping bimetal so as to carry load current and one end of the other coil is connected externally of the breaker through the shunt trip lead to the shunt trip circuit. The other coil leads are connected directly to the load terminal.

Accordingly, a primary object of the instant invention is to provide a compact circuit breaker construction in which both shunt trip and automatic overload tripping are provided in a single pole unit.

Another object is to provide a circuit breaker construction of this type in which the overload tripping means is provided with both thermal and magnetic tripping elements.

Still another object is to provide a circuit breaker construction of this type in which the terminal carrying load current is also used as a connecting point for the shunt trip coil.

These objects as well as other objects of this invention will become readily apparent after considering the following description of the accompanying drawings in which:

FIG. 1 is a side elevation of a circuit. breaker constructed in accordance with teachings of the instant invention to include both overload and shunt tripping, with one side of the housing removed to reveal the relationships between the operating elements disposed within the housing.

FIG. 2 is an exploded perspective of selected elements of the embodiment of FIG. 1.

FIGS. 3 and 4 are exploded perspectives similar to FIG. 2, showing two additional embodiments of the instant invention.

Now referring to the figures, and more particularly to FIGS. 1 and 2. Circuit breaker 10 is constructed with current carrying elements and a contact operating mechanism generally of the type described in the aforesaid U.S. Pat. No. 2,996,589. More particularly, the load current path through circuit breaker 10 consists of terminal portion 11a of terminal strap 11 positioned outside of molded housing 12, stationary contact 13 mounted on line terminal portion 11b disposed within housing 12, movable contact 14, contact arm 15, flexible conducting braid 16, bimetal l7, and flexible conducting braid 18 connected to load terminal 19 having wire grip 21 mounted thereto.

Coiled tension spring 22, connected at opposite ends I to releasable cradle 23 and contact arm 15, biases the latter upward so that the upper end thereof seats against a suitable formation on the downward extension of manual operating handle 24 which is pivotally connected by protrusion 25 to housing 12. Cradle 23 is pivotally mounted at one end thereof to internal housing protrusion 26. Latch tip 27 at the other end of cradle 23 is engageable by latch 28 at the lower end of bimetal strip 17, which is pivotally mounted near its upper end by pin 31 whose ends are journalled in internal depressions of housing 12. Coil compression spring 32 biases bimetal 17 in a clockwise direction about pin 31 as a center, with clockwise movement being limited by the engagement of the upper end of bimetal 17 with stop member 29 whose position is adjusted by screw 33. Latch 28 is insulated from bimetal 17 by spacer 35, having downwardly extending leg 36 engageable by ear 37 of magnetic armature 38 when the latter is pivoted clockwise with respect to FIG. 1 about the axis defined by projections 39 entered into apertures 41 in magnetic support frame side members 42.

Pins 43, 44, extending outward from each non-magnetic frame member 42 into internal housing recesses to operativelyposition electromagnet 50. Pole pieces 70, adjacent each member 42, are bridged by rectangular magnetic tube 45 to form a magnetic frame. Shunt trip coil 46 is wound about magnetic frame portion 45 and is provided with insulation covered flexible shunt trip lead 47 that extends through opening 48 at the load side of housing 12. The other end of coil 46 is connected directly to load terminal leg 19a enclosed within housing 12. Curved leaf spring 51 bears against one of the side magnetic support frame members 42, thereby urging the upper end of magnetic armature 38 away from magnetic frame elements 42, 42.

In operation, upon the occurrence of an overload bimetal 17 will overheat so that the lower end thereof will deflect to the right with respect to FIG. 1, moving latch 28 to the right past the rightmost portionof latch tip 27, thereby releasing cradle 23 and permitting main spring 22 to separate movable contact 14 from stationary contact 13. The energization of shunt trip coil 46 generates fluxin magnetic frame 70, 45 moving the upper end of armature 38 towards side frame members 42, causing ear 37 to engage extension 36 thereby pivoting bimetal l7 counterclockwise, with latch 28 releasing latch tip 27, so that spring 22 is effective to separate cooperating contacts 13, 14.

In the embodiments of FIGS. 3 and 4, those elements that are also found in the embodiment of FIGS. 1 and 2 are given the same numbers in all figures.

Flexible conducting braid 61 extends from the left end of coil 46 (with respect to FIG. 3) to bimetal 17 at apoint thereof in the vicinity of pivot pin 31. Shunt trip lead 47a connected to load terminal 19 extends externally of the breaker housing for connection to a shunt trip actuating switch (not shown). Thus, load current flows in series to both bimetal 17 and coil 46, thereby providing both thermal and magnetic overload protection utilizing coil 46 as part of the shunt trip mechanism connected between shunt trip lead 47a at load terminal 19. For this embodiment, a resistor (not shown) is placed in series with the shunt trip actuating switch in order to limit shunt tripping current to, say, from two to five times rated load current.

In the embodiment of FIG. 4, both shunt trip coil 63 and overload tripping coil 64 are wound about transverse magnetic frame members 45 so that currents therethrough generate fluxes that are in the same direction. Flexible conducting braid 65 connects bimetal 17 near pivot pin 31 to one end of overload tripping coil 64, whose other end is connected through lead 66 directly to load terminal 19. One end of shunt trip coil 63 is also connected through lead 66 to load terminal 19 and the other end of coil 63 is connected to shunt trip lead 47 extending externally of the breaker. Thus, the embodiment of FIG. 4 also provides thermal and magnetic overload tripping by having load current flow through bimetal 17 and coil 64 connected in series. Shunt tripping current flowing through coil 63 does not flow through overload tripping coil 64.

In both the embodiments of FIGS. 3 and 4, just as in the embodiment of FIGS. 1 and 2, the portions of the stripping circuit external of the circuit breaker are connected between shunt trip lead 47 and load terminal 19.

Although in the foregoing this invention has been described in connection with preferred embodiments,

many variations and modifications will now become apparent to those skilled in the art and it is preferred, therefore, that this invention be limited not by the specific disclosure herein but only by the appending claims.

Weclaim:

1. A circuit breaker including 'line and load terminals, a, housing, cooperating contacts disposed in said housing and connected in circuit between said terminals for carrying load circuitcurrent through said circuit breaker, an operating mechanism within said 2222:. .teztaataaasatssassesses 2; operation external to said housing, latch means normally holding said operating mechanism in contact operating position, said latch means when released releasing said operating mechanism to automatically open said contacts, overload trip means within said housing .to automatically release said latch means upon the occurrence of predetermined overload conditions in the circuit including said contacts, said overload trip means connected in circuit between said terminals, shunt trip means within said housing for releasing said latch means upon receipt of a command signal.

4. A circuit-breaker as set forth in claim 2 in which I the overload trip means also includes magnetic means, a common armature for the magnetic means of both said overload trip means and said shunt trip means.

- 5. A circuit breaker as set forth in claim 4 in which the thermal means includes a bimetal having a deflectable portion which carries the latch means and is bodily movable by the armature.

6. A circuit breaker as set forth in claim 4 in which there is a common coil for the magnetic means of both said overload trip means and said shunt trip means.

7. A circuit breaker as set forth in claim 4 in which there is an individual coil section for the magnetic means of said overload trip means and said shunt trip means, respectively.

8. A circuit breaker as set forth in claim 7 in which the thermal means includes a bimetal having a deflectable portion which carries the latch means and is bodily movable by the armature.

9. A circuit breaker as set forth in claim 1 in which both the overload trip means and the shunt trip means include magnetic means coupled to a common magnetic frame.

10. A circuit breaker as set forth in claim 9 in which the magnetic frame includes an armature operable to release the latch means, said overload trip means also including thermal means operable to release said latch means. 

1. A circuit breaker including line and load terminals, a housing, cooperating contacts disposed in said housing and connected in circuit between said terminals for carrying load circuit current through said circuit breaker, an operating mechanism within said housing for operating said contacts into and out of engagement, a handle extending from said mechanism for operation external to said housing, latch means normally holding said operating mechanism in contact operating position, said latch means when released releasing said operating mechanism to automatically open said contacts, overload trip means within said housing to automatically release said latch means upon the occurrence of predetermined overload conditions in the circuit including said contacts, said overload trip means connected in circuit between said terminals, shunt trip means within said housing for releasing said latch means upon receipt of a command signal generated external of said housing, said shunt trip means being in circuit connected directly to said load terminal.
 1. A circuit breaker including line and load terminals, a housing, cooperating contacts disposed in said housing and connected in circuit between said terminals for carrying load circuit current through said circuit breaker, an operating mechanism within said housing for operating said contacts into and out of engagement, a handle extending from said mechanism for operation external to said housing, latch means normally holding said operating mechanism in contact operating position, said latch means when released releasing said operating mechanism to automatically open said contacts, overload trip means within said housing to automatically release said latch means upon the occurrence of predetermined overload conditions in the circuit including said contacts, said overload trip means connected in circuit between said terminals, shunt trip means within said housing for releasing said latch means upon receipt of a command signal generated external of said housing, said shunt trip means being in circuit connected directly to said load terminal.
 2. A circuit breaker as set forth in claim 1, in which the overload trip means includes thermal means and the shunt trip means includes magnetic means.
 3. A circuit breaker as set forth in claim 2 in which the thermal means includes a bimetal having a deflectable portion which carries the latch means and is bodily movaBle by said magnetic means.
 4. A circuit breaker as set forth in claim 2 in which the overload trip means also includes magnetic means, a common armature for the magnetic means of both said overload trip means and said shunt trip means.
 5. A circuit breaker as set forth in claim 4 in which the thermal means includes a bimetal having a deflectable portion which carries the latch means and is bodily movable by the armature.
 6. A circuit breaker as set forth in claim 4 in which there is a common coil for the magnetic means of both said overload trip means and said shunt trip means.
 7. A circuit breaker as set forth in claim 4 in which there is an individual coil section for the magnetic means of said overload trip means and said shunt trip means, respectively.
 8. A circuit breaker as set forth in claim 7 in which the thermal means includes a bimetal having a deflectable portion which carries the latch means and is bodily movable by the armature.
 9. A circuit breaker as set forth in claim 1 in which both the overload trip means and the shunt trip means include magnetic means coupled to a common magnetic frame. 